public class ABTest{
	public static void main(String[] args){
		A a = new A();
		A b = new B();
		//B c = new A();
		//compile error if comment remove.
		String sa = a.getA();
		String sb = b.getA();
		//String sb2 = b.getB();
		System.out.println(sa);
		System.out.println(sb);
	}
}
